Cooperation between the stem cell leukemia (SCL) transcription factor and its nuclear partners LMO1 or LMO2 induces aggressive T cell acute lymphoblastic leukemia when inappropriately expressed in T cells. This study examined the cellular and molecular targets of the SCL-LMO complex at the preleukemic stage. We show that SCL and its partners are coexpressed in the most primitive thymocytes. Maturation to the pre-T cell stage is associated with a down-regulation of SCL and LMO1 and LMO2, and a concomitant up-regulation of E2A and HEB expression. Moreover, enforced expression of SCL-LMO1 inhibits T cell differentiation and recapitulates a loss of HEB function, causing a deregulation of the transition checkpoint from the CD4-CD8- to CD4+CD8+ stages. Finally, we identify the gene encoding pT alpha as a downstream target of HEB that is specifically repressed by the SCL-LMO complex.

MEK is a dual-specificity kinase that activates the extracellular signal-regulated kinase (ERK) mitogenactivated protein (MAP) kinase upon agonist binding to receptors. The ERK/MAP kinase cascade is involved in cell fate determination in many organisms. In mammals, this pathway is proposed to regulate cell growth and differentiation. Genetic studies have shown that although a single Mek gene is present in Caenorhabditis elegans, Drosophila melanogaster, and Xenopus laevis, two Mek homologs, Mek1 and Mek2, are present in the mammalian cascade. The inactivation of the Mek1 gene leads to embryonic lethality and has revealed the unique role played by Mek1 during embryogenesis. To investigate the biological function of the second homolog, we have generated mice deficient in Mek2 function. Mek2 mutant mice are viable and fertile, and they do not present flagrant morphological alteration. Although several components of the ERK/MAP kinase cascade have been implicated in thymocyte development, no such involvement was observed for MEK2, which appears to be nonessential for thymocyte differentiation and T-cell-receptor-induced proliferation and apoptosis. Altogether, our findings demonstrate that MEK2 is not necessary for the normal development of the embryo and T-cell lineages, suggesting that the loss of MEK2 can be compensated for by MEK1.The mitogen-activated protein (MAP) kinase signaling pathways consist of protein kinase cascades linking extracellular stimuli to various targets scattered in the cytoplasm, the cytoskeleton, the membrane, and the nucleus (38). There are at least three distinct MAP kinase signaling pathways in mammals, including the extracellular signal-regulated kinases (ERKs), the c-Jun N-terminal kinases, and the p38 MAP kinase (12). These kinases are activated in cascades by phosphorylation on both threonine and tyrosine residues in the regulatory TXY loop present in all MAP kinases. This phosphorylation is carried out via distinct upstream dual-specificity MAP kinase kinases (MAPKKs). The classical pathway, which appears to be the major one in growth factor signaling, uses MAP kinaseor ERK-activating kinases (MEK and MAPKK) and ERK isoforms (MAP kinase) and is named the ERK/MAP kinasesignaling pathway. In mammals, MAPKK constitutes a small family of related proteins, but only MEK1 and MEK2 are known participants in the ERK/MAP kinase cascade (38). Directly downstream of MEK1 and MEK2, ERK1 and ERK2 phosphorylate a large number of substrates located in the cytoplasm and the nucleus (13,25,27,38,45).The ERK/MAP kinase pathway is also involved in cell fate determination in Caenorhabditis elegans, Drosophila melanogaster, and Xenopus laevis (21,28,41,44). While two different MEK proteins are present in the ERK/MAP kinase cascade in mammals, a single Mek gene fulfills this role in these species. Sequence analysis revealed that the murine MEK1 protein is more related to the Xenopus MEK than to the mouse MEK2.Indeed, MEK2 protein is only 80% identical and 90% similar to MEK1, whereas Xenopus MEK is 91% i...

Objective To identify genes that may participate in the pathophysiology of Sjögren's syndrome (SS), the technique of differential display was applied to labial minor salivary gland (MSG) biopsy samples. Methods Total RNA was isolated from MSG biopsy samples from a woman with primary SS and a control subject, and the differential display protocol with 8 different random oligonucleotide primers was performed. One particular differentially expressed fragment showed 98% homology with the cysteine‐rich secretory protein 3 (CRISP‐3) gene. The result was verified by reverse transcription‐polymerase chain reaction (RT‐PCR) with messenger RNA (mRNA) samples from MSG biopsy tissues obtained from 4 women with primary SS. A CRISP‐3 RNA probe was synthesized for in situ hybridization of 7 MSG biopsy samples from patients with primary SS. In an attempt to interpret the expression of CRISP‐3, normal peripheral blood lymphocytes (PBLs) were activated in vitro at different time points and assayed for CRISP‐3 expression. Finally, B cells were transfected with the coding region of CRISP‐3 and monitored for the up‐regulation of different B cell activation markers. Results The CRISP‐3 gene was detected by RT‐PCR in all SS patients tested. Mainly the mononuclear cells infiltrating the MSGs of patients expressed CRISP‐3 mRNA. In addition, CRISP‐3 was detected by RT‐PCR between 30 minutes and 6 hours in phorbol myristate acetate‐activated normal PBLs, while staurosporine inhibited this expression. CRISP‐3‐transfected B cells exhibited an up‐regulation in CD25 surface expression. Conclusion The CRISP‐3 gene is identified as a novel early response gene that may participate in the pathophysiology of the autoimmune lesions of SS.

sTNFR-1 and angiogenin represent potential blood markers for endometriosis.